This invention is concerned with improvements in or relating to the manufacture of shoes and is especially concerned with methods and apparatus for attaching components such as heels to shoes.
The term "shoe" where used herein is to be understood as referring to outer footwear generally whether complete or in the course of manufacture.
It is a common practice in the shoe industry to attach heels by means of nails which are hammered through the insole of the shoe into the heel. In most cases, if four or six nails are used, adequate heel attachment can be achieved whether the heel is made of wood or of thermoplastic material. However, in some circumstances, adequate heel attachment is difficult to achieve. For example, in the case of sharply tapering heels, e.g. stiletto heels, which are generally made of thermoplastic material since wood is not sufficiently strong, it may be difficult to insert a sufficient number of nails in the limited area available. The area available is limited by the taper of the heel which reduces the area where there is sufficient depth of material for each nail to be inserted. The nailing area available may also be reduced by the presence of a shank in the shoe.
It is one of the various objects of the present invention to provide an improved method of attaching a heel which comprises thermoplastic material to a shoe, which method enables a fastener to be embedded in the thermoplastic material of the heel.
There is hereinafter described in detail an apparatus suitable for use in attaching a heel which comprises thermoplastic material to a shoe, this apparatus being illustrative of the invention in its apparatus aspects. There is also hereinafter described in detail a method of using the illustrative apparatus to attach such a heel to a shoe, this method being illustrative of the invention in its method aspects.
The illustrative apparatus comprises a gauge plate in the shape of the heel seat of a shoe which provides shoe locating means whereby a shoe can be located for a heel to be attached thereto by being fitted over the gauge plate. The illustrative apparatus also comprises clamping means whereby a heel to be attached can be clamped against the heel seat of a shoe located by the gauge plate. The clamping means comprises a pad arranged to engage the ground-engageable surface of the heel, a pad arranged to engage a rear surface of the heel, and a piston and cylinder assembly arranged to press the pads against the heel.
The illustrative apparatus also comprises heating means in the form of electric cartridge heaters which are arranged to heat a fastener having a head portion and a shank portion to a temperature above the softening temperature of the thermoplastic material of the heel. The heaters are arranged to heat the fastener while it is contained in a magazine of the illustrative apparatus. The particular fastener used with the illustrative apparatus is preferably in the form of a staple having a head and four shank portions.
The illustrative apparatus also comprises fastener locating means whereby a fastener heated by the heating means can be appropriately located for insertion through the insole of a shoe located by the gauge plate and into a heel thereof. The fastener locating means comprises a bush made of a heat-insulating material in which the heated fastener can be positioned prior to the shoe being located by means of the gauge plate. When located in the bush, a fastener rests on a pusher which is movable by insertion means of the illustrative apparatus in the form of a piston and cylinder assembly. The insertion means is operable to insert a fastener located by the bush through the insole of a shoe located by the gauge plate so that the fastener shank portion passes through the insole and into the thermoplastic material of the heel. The insertion means causes the pusher to press the fastener while heated through the insole and into the heel.
In the illustrative method of attaching a heel which comprises thermoplastic material to a shoe, the fastener to be used is heated to a temperature above the softening temperature of the thermoplastic material of the heel, the heated fastener is located for insertion using the fastener locating means, the heel is located against the heel seat of the shoe, the heel is clamped in position on the located shoe as by using the clamping means referred to, and the heated fastener is then inserted by the insertion means so that the shank portions of the fastener pass through an insole of the shoe and are pressed into the thermoplastic material of the heel, heat from the fastener causing the thermoplastic material to soften thereby allowing the shank portions to enter the material and become firmly embedded therein when the fastener and material have cooled.